Conventional Vee bearings, by definition, provide spaced pairs of line contact bearing elements against which a semi-cylindrical area of a cylindrical profile, such as a tool or workpiece, is biased for rotation and/or reciprocating infeeding motion relative thereto. The pair spacing is along the axis of the cylindrical profile with the line contact bearing elements of each pair spaced less than 180.degree. about the cylindrical profile to be biased thereagainst, i.e., each pair bears against the same semi-cylindrical surface area of the journaled cylindrical profile. Accordingly, rotation or reciprocation of the cylindrical profile will necessarily occur about or along a bearing or journal axis concentric with its cylindrical surface subject only to the requirement that the cylindrical surface be maintained in constant engagement with the line contact bearing elements.
The universally recognized advantage in the use of Vee bearings is that they are a fixed part of a static machining support whose V journal profile, defined by the spaced, bearing element pairs, will always define precisely the same journal axis for those cylindrical profiles having a common diameter thus eliminating the introduction of those positioning errors inherent in the chucking and unchucking of tools or workpieces. Where diamonds are employed as the line contact bearing elements the possibility of wear is eliminated making it virtually impossible to introduce any positioning error into a Vee bearing. A more detailed discussion of the advantages inherent in the use of Vee bearings is contained in U.S. Pat. No. 3,679,273 whose disclosure is herein incorporated by reference.
The known disadvantages in conventional Vee bearing design vis-a-vis the use of a chuck or collet is that cylindrical profiles of different diameters could not, heretofore, be journaled in the same Vee bearing for rotation or reciprocation along a common centerline. Accordingly, it has previously been necessary to insure that the spindles of any tools which were to be interchanged in the same Vee bearing, for the performance of multiple machining operations along a common centerline, be of uniform diameter.
One purpose of the present invention is to provide, in a Vee bearing, the versatility of a chuck or collet as regards substitution of different size spindles while retaining the advantages of the Vee bearing in the avoidance of both static positioning and kinetic machining eccentricities necessarily inherent in any chucked tool. The foregoing is particularly important in micromachining because even those minor positioning errors and/or eccentricities inherent to chucked tools, which may be tolerated in macromachining, are multiplied beyond permissible tolerance ranges in the case of micromachining operations.
A further purpose of the invention is to expand the range of a conventional Vee bearing function in the use of the same to perform multiple machining operations along spaced, parallel centerlines without the necessity for repositioning either the workpiece or bearing. Exemplary of this latter conventional function is the drilling of spaced, inline holes by sequential substitution of different size drill spindles in the same fixed Vee bearing. When using a single fixed Vee bearing the number of inline holes that can be drilled without repositioning the workpiece is, of course, limited as a function of the desired hole spacing, the different size drill spindles available and the gross dimensions of the Vee bearing whereas, in accordance with the present invention, this particular range of usage is greatly amplified.